Accumulator vent valve for free piston engines



Nov. 30, 1954 HUBER 2,695,601

ACCUMULATOR "ENT VALVE FOR FREE PISTON ENGINES Filed Aug. 14, 1953 Fig.

I/VVE/VTUR R B RT H u BER United States Patent ACCUMULATOR VENT VALVE FOR FREE PISTON ENGINES Robert Huber, Bellevue, France, assiguor to Societe dEtudes et de Participatious, Eau, Gaz, Electricite, Eng-fir}, S. A., Geneva, Switzerland, a society of Switzer Application August 14, 1953, Serial No. 374,274 Claims priority, application France June 11, 1953 3 Claims. (Cl. 123-46) The present invention relates to free piston machines including a return energy pneumatic accumulator. Such machines include at least one powigaiston (and generally two power pistons running in oppo directions) movable in a power cylinder and rigid with another piston movable in a compressor cylinder, the energy produced by the combustion of fuel in the power cylinder causing both of the pistons to move outwardly, whereas the inward strokes of the pistons are produced by the energy which, during every preceding outward stroke, was stored up in an air cushion belonging to a return energy pneumatic accumulator.

In free piston machines, at least one of the dead center positions of the piston or pistons is not fixed by mechanical means, but on the contrary depends exclusively upon the balance of the forces acting thereon, so that said positions may undergo variations according to the conditions under which the machine is working. Such free piston machines may be of two kinds, to wit wholly free piston machines in which both of the dead center positions (that is to say the outer dead center position and the inner dead center position) of each of sets of pistons are free from mechanical control and semi-free piston machines in which only one of the dead center positions and generally the inner one is free from mechanical control and determined merely by the balance of forces acting thereon, whereas the other dead center position is fixed by mechanical means.

The object of my invention is to provide a machine of this kind which is better adapted to meet the requirements of practice than those used for the same purposes up to the present time.

My invention consists chiefly in providing the return energy pneumatic accumulator with a discharge aperture and in controlling this aperture by an automatic device responsive to variations of a phenomenon produced by the oscillatory or reciprocating movement of the pistons 1 so that this discharge aperture remains closed as long as said oscillatory movement is taking place and is automatically opened when this reciprocating oscillatory movement stops.

Other features of my invention will become apparent in the course of the following detailed description of a specific embodiment thereof with reference to the accompanying drawings, given merely by way of example, and in which:

Fig. 1 diagrammatically shows a wholly free piston auto-generator having opposed cylinders and made according to my invention, the left hand side'of this machine being not visible.

Fig. 2 shows on an enlarged scale the automatic discharge device associated with one of the pneumatic energy return accumulators of the machine of Fig. 1.

in the following description with reference to the drawings, it will be supposed that the invention is applied to the case of a free piston auto-generator including opposed sets of pistons which are wholly free from mechanical control.

The general construction of the auto-generator may be of any suitable conventional kind. For instance, as shown by Fig. 1, this machine includes a power cylinder 1 in which are slidably mounted two power pistons 2 moving in opposed directions. Each power piston 2 is rigid with a piston 3 working in a compressor cylinder 4. The two sets of free pistons 2, 3, only one of which is Wholly shown in 2,695,601 Patented Nov. 30, 1954 ice 2 Fig. 1, are connected together, synchronizing device which is m In the wall of the power cylinder are provided, on the one hand a system of apertures 5 which :are intake apertures for the air used to feed and scavenge the power cylinder and, on the other hand, a set of apertures 6, which are the discharge apertures of the power cylinder. These apertures are controlled by pistons 2, which clear them when they are close to their outer dead center position. in the middle transverse plane of power cylinder 1, there 18 prov ded at least one fuel injector 7 through which fuel is introduced into the power cylinder when pistons 2 are close to their inner dead center position.

Thus, the power portion of the auto-generator works on a two-stroke diesel cycle.

Each of the compressor pistons 3 divides the cylinder 4 m which it is running into two compartments 4a, 4b. The annular compartment 4a, which is located on the inner side of the piston, constitutes the power cylinder proper and is 'fitted with inlet valves 8a and discharge valves 8b. Compartment 4b, which is on the outer side of piston 3, belongs to the return energy pneumatic accumulator and contains an air cushion.

When the free pistons, under the eifect of the combustlon of fuel in power cylinder 1, are working outwardly, compressor pistons 3 suck in air through valves 8a into compartment 4a/and simultaneously compress the mass of air which forms the air cushion in compartment 4b. When the pistons have reached their outer dead center position, their movement is reversed under the effect of the pressure of the air cushion present in compartment 4b and they now move toward their inner dead center posltron. During this return stroke, the air which has been sucked in into compartment 4a is compressed and in known fashion, by a not visible on the drawdischarged past valves 8b into a casing 9 which sur- 7 rounds power cylinder 1 and which constitutes an air reservoir. During the next outward stroke of the pistons, the compressed air present in casing 9 enters power cylinder 1 through apertures 5 and flows out therefrom through apertures 6, whereby power cylinder 1 is scavenged and fed with fresh air. The gaseous mixture which is delivered through the apertures 6 of the power cylinder and which is both at a high pressure and a high temperature constitutes a power gas fed to a turbine or another machine to be driven by this power gas.

It is already known to discharge accumulator 4b by means of a special valve (which is not shown by the drawing) when the machine is stopped by operating the stopping member provided for this purpose and which for instance stops the injection of fuel to the power cylinder. However, in known machines this discharge valve remains closed when an accidental stopping of the machine takes place. In this case, the pressure in casing 9 and in power cylinder I quickly drops, whereas accumulator 4b remains full of air under pressure. It follows that pistons 2, 3, under the efiect of this air pressure and of the pressure drop in spaces 1 and 9, move toward the center of the machine. As the central portions of the cooling jacket of the power cylinder are cooled quicker than the pistons 2 themselves, it often happens that the pistons remain jammed at the center of the machine, which prevents restarting of said machine.

In order to avoid this drawback of known machines, such as they exist at the present time, I provide, according to my invention, a discharge aperture in the return energy pneumatic accumulator, and this discharge aperture is controlled automatically by a device responsive to the reciprocating or oscillatory movement of the pistons, in such manner that said discharge aperture remains closed as long as said oscillatory movement is taking place and is opened when this movement stops.

The way in which the reciprocating movement of the pistons acts on said aperture may be of any kind whatever. For instance, I may connect with one of the pistons or with a part oscillating together with the pistons, for instance a portion of the synchronizing means above re ferred to, one of the main elements of a system producing by induction an electric current. This current is intended to act upon a relay which keeps the return energy pneumatic accumulator discharge aperture closed as long as current is being produced, that is to say as long as the oscillatory movement of the pistons is taking place. The discharge aperture is arranged to be opened as soon as said current stops, a delay device being advantageously provided to act on said discharge aperture so as to prevent it from being opened in response to the very short stop which takes place every time the pistons are at the ends of their strokes, that is in dead center position.

I may also make use, to control the automatic discharge device, of the pressure of pressures resulting from the movement of the pistons.

An advantageous embodiment of this kind is shown by Figs. 1 and 2. As shown by these figures, the return energy pneumatic accumulator 4b is provided with a discharge aperture controlled by a valve consisting of a piston 11 the end face of which may be applied against aperture 10 so as to stop it. Piston 11 is rigid with another piston 12 of larger diameter, which is movable in a cylinder 13 located inside accumulator 4b. Piston 12 divides the inside of cylinder 13 into two chambers 13a and 13b each of which communicates, through a check valve, with the inside of accumulator 4b. The check valve 14a of chamber 13a is arranged to enable air under pressure present in accumulator 4b to enter chamber 13a, whereas the check valve 14b of chamber 13b is arranged to enable the air of chamber 13b to flow out toward the inside of accumulator 4b. Chambers 13a and 13b communicate together through a narrow channel 14 provided either in piston 12 (Fig. 2) or in the wall of cylinder 13. A spring 16 acts upon piston 12 in the direction which causes aperture 10 to be opened.

As long as the set of pistons 2, 3 is oscillating, that is to say during normal working of the machine, a pressure corresponding to the maximum pressure in accumulator 4b exists in chamber 13a, whereas a pressure corresponding to the minimum pressure in said accumulator 4b exists in chamber 13b. Piston 11 is thus applied against aperture 10 and keeps it closed. On the contrary, if the set of pistons 2, 3 ceases to oscillate, the pressure in chambers 13a and 13b become equal owing to the provision of channel 15 and spring 16 is then free to open aperture 10 whereby the air cushion present in accumulator 4b is discharged to the outside.

Of course, during the stopping of pistons 2, 3 and the opening of orifice 10 by piston 11, a short time elapses, say one second or even less, which is necessary in order to avoid orifice 10 being opened every time the pistons 2, 3 are reaching their dead center positions, where they stop for a very short time during normal oscillation movement.

This discharge of accumulator 4b, obtained as above described when pistons 2, 3 stop for some accidental reason, always takes place sufiiciently early to prevent the pistons 2, 3 from moving toward the center of the machine where they would remain jammed for reasons above stated.

In a general manner, while I have, in the above description, disclosed what I deem to be practical and efiicient embodiments of my invention, it should be Well understood that I do not wish .to be limited thereto as there might be changes made in the arrangement, disposition and form ofv the parts without departing from the principle of the present invention as comprehended within the scope of the accompanying claims. i

What I claim is:

1. A free piston machine including a power cylinder,

4 a compressor cylinder fixed with respect to said power cylinder, free piston means including a power piston and a compressor piston rigid with each other and movable in said power and compressor cylinders respectively, pneumatic accumulator means forming a closed chamber in cooperating relation to said piston means to constitute an air cushion compressed during the outward strokes of said piston means and to restore the energy thus accumulated to said piston means for the inward strokes thereof, said pneumatic accumulator means being provided with a discharge aperture, and means responsive to the reciprocating movement of said piston means to keep said aperture closed as long as. said movement is taking place and to open said aperture as soon as said reciprocating movement ceases.

2. A free piston machine including a power cylinder, a compressor cylinder fixed with respect to said power cylinder, free piston means including a power piston and a compressor piston rigid with each other and movable in I said power and compressor cylinders respectively, pneumatic accumulator means forming a closed chamber in cooperatlng relation to sand piston means to constltute an air cushion compressed during the outward strokes of said piston means and to restore the energy thus accumulated to said piston means for the inward strokes thereof, said pneumatic accumulator means being provided with a discharge aperture, and means responsive to variations of the pressure of the air cushion in said closed chamber to keep said aperture closed as long as said pressure variations are taking place and to open said ap'erture as soon as pressure variations are no longer occurring in said closed chamber.

3. A free piston machine including a power cylinder, a compressor cylinder fixed with respect to said power cylinder, free piston means including a power piston and a compressor piston rigid with each other and movable in said power and compressor cylinders respectively, pneumatic accumulator means forming a closed chamber in cooperating relation to said piston means to constitute an air cushion compressed during the outward strokes of said piston means and to restore the energy thus accumulated to said piston means for the inward strokes thereof, said pneumatic accumulator means being provided with a discharge aperture, a closed cylinder mounted inside said closed chamber, a piston movable in said last mentioned cylinder, a valve rod carried by said piston for controlling said aperture, said last mentioned piston dividing said last mentioned cylinder into two opposed chambers, check valve means provided in the walls of said last mentioned cylinder to connect said last mentioned chambers with the inside of said pneumatic accumulator closed chamber, said check valve means being mounted to form in one of said opposed chambers a pressure equal to the maximum pressure in said pneumatic accumulator closed chamber and in the other of said opposed chambers a pressure equal to the minimum pressure in said pneumatic accumulator closed chamber, the difference between said pressure being arranged to keep said stem applied against said aperture so as to close it, resilient means for urging said last mentioned piston in the opposed direction so as to open said aperture, and a channel of restricted cross section connecting said two opposed chambers together, whereby the pressures in said opposed chambers become equal as soon as pressure variations are no longer occurring in the re turn energy accumulator closed chamber.

No references cited. 

